PubMed1985
The addition of small amounts of high mol. wt polymers to a fluid moving through a pipe typically increases fluid viscosity and thereby diminishes the rate of flow. Under appropriate conditions of flow, however, the addition of linear polymers of high mol. wt--of the order of 10(5) to 10(7) daltons--may cause the flow to increase as much as 3-fold and occasionally more without altering the driving pressure. This effect, generally known to hydrodynamicists under the rubric 'Toms phenomenon' or as 'polymer drag reduction', generally occurs at high (greater than 1000) Reynolds numbers. However, flow also increases at much lower Reynolds numbers under certain conditions, including oscillatory, pulsatile, and helicoidal flows and flow through a column of sand. The Toms phenomenon has been repeatedly observed in various types of flow with both aqueous and organic solvents in combination with a wide variety of polymer additives. A marked fall in the pressure gradients of constant blood flows through pipes has also been observed upon the addition of polyacrylamide, poly(ethylene oxide), deoxyribonucleic acid, or a polysaccharide extracted from okra. It is the consensus among students of fluid mechanics that linear macromolecules suppress flow disturbances by stabilizing or laminizing the dynamic fluid structure when rod- or thread-like particles align themselves parallel to the axis of flow. Mostardi et al. demonstrated with hot film anemometry that aortic flow instabilities downstream from a temporary partial occlusion are dampened after infusion of a polymer drag-reducing agent, Separan AP-30 (Dow Chemical Co.).(ABSTRACT TRUNCATED AT 250 WORDS)